1. Field of the Invention
The present invention relates to an organic EL panel (organic electroluminescence panel) promising in broad applications as flat panel displays for use in televisions, personal computer monitors, hand held devices such as mobile phones, as well as surface emitting light sources, illuminations, emitting type advertisement bodies, and the like.
2. Description of the Related Art
Organic EL panels have been expected as flat panel displays which can replace cathode ray tubes and liquid crystal displays in light of advantages of wide viewing angle, high response speed, low electric power consumption and the like.
Organic EL panels have a structure including an electrode for anode, an electrode for cathode and an organic light emitting medium layer arranged therebetween, and are self-emitting display devices which permit emission at the organic light emitting medium layer by applying voltage between the electrodes to allow an electric current to flow. In general, it is constructed such that a transparent electrode is used as the anode, and the light generated at the organic light emitting medium layer is extracted from the transparent anode side.
Furthermore, illustrative examples of driving system of the display include passive matrix driving and active matrix driving. In order for the display to have enlarged size and higher definition, active matrix driving in which display pixels that construct the display are driven by a TFT (thin film transistor) for every picture element is advantageous in terms of capability of driving at a low voltage. However, according to conventional-type bottom emission devices produced by forming the transparent anode on the TFT board to extract the light from the transparent anode side, there has been disadvantageous in that TFT, wiring and the like may limit the aperture ratio, thereby decreasing efficiency of extraction of the light.
To the contrary, so-called top emission panels have been recently developed in which a transparent electrode is used as the cathode, or the anode electrode and the cathode electrode are formed in the reverse order. Because the top emission panel can achieve greater aperture ratio as compared with conventional bottom emission panels, efficiency of extraction of the light is reported to be improved (for example, see Patent Document 1).
In such instances, cap sealing, which is a common sealing process of the bottom emission organic EL panels, using a glass cap or a metal cap having a recessed part is not applicable to the top emission panel because of internally included nontranslucent desiccant agent. Therefore, in recent years, solid sealing carried out by laminating a passivation film on the organic EL panel, followed by attaching a transparent substrate thereon via an adhesive was proposed (for example, see Patent Document 2).
However, according to the solid sealing method as described above, the desiccant agent cannot be included internally. Thus, film thinning, moisture permeability lowering and frame area widening of the adhesive layer as well as moisture permeability lowering of the passivation film shall be mandatory for suppressing penetration of water from the end face of the adhesive layer. Therefore, to attain a sealing performance that satisfies demands for narrowing of the frame area in recent years was difficult.
The invention was made in order to solve the aforementioned problems, and an object of the invention is to provide an organic EL panel which enables transparent sealing accompanied by low moisture permeability, and can be also used for sealing the top emission panel without deterioration for a long period of time even in the case of the panel having a narrow frame area.
Patent Document 1: JP-A-2001-43980
Patent Document 2: JP-A-2004-95551